Known methods of fractionation technologies of fat or oil include a solvent fractionation method and dry fractionation method. While the fractionation technology as used herein means a technology for separating fat or oil into a crystal fraction and a liquid fraction by taking advantage of differences in crystallization characteristics, fractionation performance between a crystal fraction and a liquid fraction differs depending on a particular fractionation method. In a solvent fractionation method, fat or oil is dissolved by adding 0.5 to 5 times larger volume of a solvent (such as acetone, hexane and alcohols), and crystals are precipitated by cooling the resulting solution to separate a crystal fraction. The fractionation performance between a crystal fraction and a liquid fraction is quite excellent, and the amount of a residual liquid component in a crystal portion is usually low as compared with a dry fractionation method. However, the production cost by a solvent fractionation method is high as compared with a dry fractionation method since this method requires confirmation for safety ascribed to the use of the solvent.
While yields of a crystal fraction and a liquid fraction can be controlled by a fractionation temperature in a dry fractionation method, the amount of residual liquid components in a crystal fraction is quite high as compared with a solvent fractionation method since no solvent is used for solid-liquid separation by pressing or filter press. Therefore, it has been impossible to reduce the amount of a residual liquid component after solid-liquid separation. While the residual amount of a liquid component largely affects the quality of fat or oil used as hard butter, it has not been easy to solve the problem.